The present subject matter relates to the fields of peptide and polypeptide selection, immunology, and contraception in animals. In particular, the present subject matter relates to peptides and polypeptides that bind to the zona pellucida (ZP) of oocytes (e.g., canine oocytes), methods for selecting such peptides and polypeptides, and pharmaceutical compositions that comprise such peptides and polypeptides (e.g., for inducing an immune response against sperm). The pharmaceutical compositions may include immunogenic compositions and vaccines that may be administered to animals such as canines for immunocontraception.
“Capture and kill,” the primary strategy used to control unwanted dog populations, has not reduced the magnitude of this serious problem in 100 years because it illogically addresses the result rather than the cause of the problem. The obvious solution is preventing the birth of unwanted animals. Surgical gonadectomy is considered the gold standard and low cost spay/neuter clinics have made limited progress in reducing unwanted dog populations in some locals, but it is not equal to this overwhelming task. Clearly, an effective, technically uncomplicated and inexpensive method applied on a mass scale is needed. In spite of recurring claims for new wonder drugs, none have met the challenge. For example, the current attention is focused on an industrial chemical (vinylcyclohexene dioxide) which kills primordial cells of ovarian follicles. Unfortunately, based on tests of the National Toxicology Program of the National Institute of Environmental Health Sciences, The International Agency for Research on Cancer (IARC) of the World Health Organization has classified this chemical as a carcinogen, and its production has been discontinued world wide. Some chemical, hormonal and vaccine contraceptive strategies have had limited success, and likely solutions will come from incremental improvement of these proven technologies. Zona pellucida (ZP) derived from pig ovaries (pZP) has been studied as an antigen for contraceptive vaccines for decades and shown to be highly successful for some species, but it is highly variable and frequently ineffective in dogs. Here, using powerful, cutting edge phage display technology, we isolate canine specific zone pellucida (cZP) binding peptides for use as antigens in immunogenic compositions and vaccines to block fertilization in dogs.